Method of reducing the aflatoxin contact of oilseed meal products

ABSTRACT

There is disclosed a method of reducing the aflatoxin content of an contaminated oilseed meal products. A homogeneous mixture comprising the product, from 10 to 40 percent by weight of water, at least one oxide and/or hydroxide of an alkali metal or alkaline earth metal, and at least one organic amine is formed. The quantity of oxide and/or hydroxide is such that the mixture has a pH of at least 8. The quantity of organic amine is such that this pH is raised to at least 9.5 percent. The mixture is reacted at a temperature below 150*C to reduce the aflatoxin content of the mixture to less than 100 parts per thousand million. The detoxified mixture is then dried.

United States Patent [191 Brandt et al.

[ June 17, 1975 [73] Assignee: Etablissements V.Q. Petersen & Cie,

Senegal [22] Filed: Feb. 12, 1974 [21] Appl. No.: 441,741

, 1 [30] Foreign Application Priority Data Feb. 13, 1973 Switzerland2005/73 [52] US. Cl 426/321; 426/373 [51] Int. Cl A23k 1/00 [58] Fieldof Search 426/374, 373, 286, 321,

[56] References Cited UNITED STATES PATENTS 3,429,709 2/1969 Masri etal. 426/335 6/197] Mann etal ..426/374 9/1972 Espoy 426/374 PrimaryExaminerNorman Yudkoff Assistant ExaminerHiram H. Bernstein Attorney,Agent, or FirmRobert E. Burns; Emmanuel J. Lobato; Bruce L. Adams [5 7]ABSTRACT There is disclosed a method of reducing the aflatoxin contentof an contaminated oilseed meal products. A homogeneous mixturecomprising the product, from 10 to 40 percent by weight-of water, atleast one oxide and/or hydroxide of an alkali metal or alkaline earthmetal, and at least one organic amine is formed. The quantity of oxideand/or hydroxide is such that the mixture has a pH of at least 8. Thequantity of organic amine is such that this pH is raised to at least 9.5percent. The mixture is reacted at a temperature below 150C to reducethe aflatoxin content of the mixture to less than 100 parts per thousandmillion. The detoxified mixture is then dried.

15 Claims, N0 Drawings METHOD OF REDUCING THE AF LATOXIN CONTACT OFOILSEED MEAL PRODUCTS BACKGROUND OF THE INVENTION The invention relatesto a method of reducing the aflatoxin content of an oilseed meals.

Aflatoxins B B G G are highly toxic metabolites developed by certainmoulds, more particularly by Aspergillus F lavus. The latter mould growson peanut-oil seed, cottonseed and other seeds in tropical climateshaving a relative humidity of more than 85 percnt. Aflatoxins are verystable chemically, owing to their molecular structure. They are notaffected by thermal treatment at 160C for an hour.

Among the aforementioned aflatoxins, aflatoxin B is considered the mosttoxic and is most frequently present in cakes of oil-bearing seeds andother products liable to be infected by Aspergillus Flavus. Theaflatoxin can be detoxified only by profoundly modifying the originalchemical structure of the toxin. Research has shown, however, that it isnot sufficient to open the lactone ring (shown in analysis by thedisappearance of the fluorescent chromatographic spots characteristic ofaflatoxin) since, as can be shown, the molecule can revert to itsoriginal form and become toxic again. The molecule must be destroyed byoxidizing certain parts of it (the double bonds in the ring), in whichcase the starting substance must be the open lactone ring form.Experience shows that though the ring is opened by alkalinity ingeneral, it is oxidized only by alkalinity produced by certain strongalkalis.

Food contaminated by aflatoxins is unsuitable for consumption. The F.A.O. have fixed the total quantity of aflatoxin acceptable in animalfood at 50 ppb. The abbreviation ppb means parts per billion, which isequivalent to mg/ tonne. The term billion, as used herein, means1,000,000,000. This limit is much lower than the 200 to 1000 ppbfrequently found in contaminated peanuts or peanut oil cakes. Peanut oilcakes are an important substance in fodder for animals such as cattleand poultry, and consequently much research has been done in order tofind means of decontamination.

It has been proposed, for example, to use the fermentation method. Somemicro-organisms are capable of metabolizing (destroying) aflatoxins,using as substrate the polysaccharides present in the oil cakes. Thismethod has the disadvantage of requiring expensive installations andrelatively long treatment. It is used in certain industrial countriessuch as France, where the climate is less humid and Aspergillus Flavuscannot start growing again from its spores.

It has also been proposed to use an extraction method and organicsolvents. A number of organic solvents such as methanol, ethanol,acetone and chloroform can extract aflatoxin from oil cakes. This methodrequires expensive installations and may be dangerous, since thesolvents are inflammable. It has the further disadvantage of eliminatingother fatty residues in the oil cakes, thus lowering their nutritionalvalue.

Methods of detoxication have also been proposed wherein use is made ofchemical products capable of converting aflatoxins. Although manychemical agents can react with aflatoxins, use can be made of only afew, either because they are themselves toxic or because theyexcessively reduce the nutritional value of the products treated, orbecause they are too expensive.

Strong bases are the most effective. They hydrolyze the lactone inaflatoxins and form the corresponding salt of the carboxyl group and thephenolate:

In this form, aflatoxins slowly oxidise in air and disappear from theoil cakes in a few weeks.

In one known method (U.S. Pat. No. 3,429,709) the reagent used isammonia. Ammonia, however, is not a sufficiently strong base; it is veryvolatile and cannot be used at ambient pressure and at a temperature of100C. The pH of a hydrated product (20% water) is of the order of 8.5 to9 before heating but falls to 88.5 during treatment at -l00C.

It has also been proposed (U.S. Pat. No. 3,585,041) to use methylaminewhich is less volatile than ammonia and gives a pH which is 1 to 1.5 pHunits greater than that given by the same molecular concentration ofammonia i.e. methylamine is about 20 times as strong a base. However, itis very disadvantageous to use methylamine in the proposed proportions(0.6-1.5 percent of the weight of the contaminated product), since it isdifficult to eliminate the methylamine from the product, which acquiresa pungent smell and disagreeable taste which persists even after vacuumtreatment or exposure to air for several weeks. Probably methylaminebecomes relatively strongly fixed to the acid (COOH) groups of theproteins.

The object of the invention is to provide a method which, though usingan organic amine as the reagent, obviates the aforementioneddisadvantage of the known method.

SUMMARY OF THE INVENTION The method according to the invention comprisesforming a homogeneous mixture comprising: the crushed oil seeds, from 10to 40 percent by weight of water, at least one basic agent selected fromthe group consisting of the oxides and hydroxides of alkali metals andalkaline earth metals in an amount such that the homogeneous mixture hasa pH of at least 8, and at least one organic amine in an amountsufficient to further raise the pH to at least 9.5; reacting thehomogeneous mixture by maintaining the mixture at a temperature below150C for a time sufficient to reduce the aflatoxin content of theproduct to less than ppb; and drying the resulting detoxified product toreduce its water content.

The method of the invention is applicable to contaminated agriculturalproducts of animal or plant origin, e.g. the products disclosed in US.Pat. Nos. 3,429,709

' vantageof providing high alkalinity (pK and 3,585 ,041. The productsshould have a fats content of less than 10 percent.

' agentjand a volatile highly basic agent, used in minimumconcentration. The non-volatile basic agent, namely the oxideor'hydroxide of an alkali metal (e.g. sodium or potassium) oralkaline-earth metal (e.g. calcium), neutralizes the natural buffereffect of proteins and gives a minimum basic pH providing the conditionsunder which the aflatoxin is chemically modified. Suitable non-volatilebasic agents include calcium oxide or hydroxide and sodium and potassiumhydroxides. The volatile basic agent, used in small quantities, providesthe excess basicit'y. for ensuring the rapid, complete destruction ofthe aflatoxins. Subsequently, the volatile agent is eliminated byevaporation (drying) together with the water added to the product beforeprocessing.

' The volatile agent is an organic amine, for example methylamine,,dimethylamine, trimethylamine, ethylamin e;,;or a mixture thereof.

Methylarnine is preferably used, since it has the ad- 3.37 at 25C), an dhas a relatively high boiling point (6.3C) compared with, for exampleammonia, but can still be subsequently eliminated by evaporation.

The use of a non-volatile basic agent, to increase the pH of the productto at least 8, allows a very substantial reduction of the amount of thevolatile agent to be used; As a matter of fact, tests have shown thatalready 0.1 percent by weight of an amine permits a hydrolysis reactionand destruction of aflatoxins to be achieved in a satisfactory manner.These tests have likewise shown that the maximum useful amount ofvolatile agent, namely the amount necessary to raise the pH to theoptimuin value for the reaction, is situated at 0.6 percent.lndeed',"fan increase in the amount of volatile agent aboveii6 percentdoes not have an appreciable effect on the elevation of the pH andconsequently at the efficacy of the reaction.

Very small quantities of amine, less than the minimum quantity usable inthe known methods, can consequently be used owing to the presence of thenonvolatile basic agent.

The non-volatile base, besides acting in the manner described,facilitates the volatilization of the volatile base, since the naturalacid groups in the product remain preferentially blocked by thenon-volatile base.

Drying to reduce the moisture content of the detoxified product to adesired value, especially to between 5 and percent, can be acceleratedby crushing the product into coarse meal.

The basicity of the product after drying is due mainly to the presenceof the non-volatile base. Neutralization can be carried out by adding anorganic or inorganic EXAMPLE 1' 30 g of slaked lime was mixed with l 500g of crushed peanut oil cake containing 2,000 ppb of aflatoxin. Asolution of 24 ml of 40 percent methylamine diluted in 255 ml water wasadded as uniformly as possible to the oil cake. The mixture, which has apH of approximately 10, was then extruded while cold to form compactpellets. The extruder body was cooled so that the pellets leave it at arelatively low temperature in order to prevent premature evaporation ofwater and methylamine.

The pellets were stored at ambient temperature for 15 days and crushedand dried in the open air for 2 days in order to reduce their watercontent to about 9 percent. The aflatoxin content of the pellets wasbelow 100 ppb (100 mg/tonne).

EXAMPLE 2 30 g of slaked lime was mixed with 1500 g of crushed peanutoil cake containing 900 ppb of aflatoxins. A solution of 12 ml of 40percent dimethylamine, diluted in 255 ml water was added to the oilcake. The mixture, which had a pH of approximately 9.7 was extrudedwhile cold, forming comptact pellets which were then heated to 100C for2 hours at normal pressure. The

pellets were crushed and dried in an oven at C for.

4 hours in order to reduce their water content to about 6 percent. Theproportion of aflatoxin destroyed was about percent.

As the preceding Examples show, the length of the detoxification processis inversely proportional to the temperature thereof. The duration canbe further reduced by detoxification at a pressure above atmosphericpressure, thus avoiding losses of water vapour and gaseous amine. Thelength of detoxification can be reduced to less than 10 minutes byperforming the reaction at a temperature between 70 and C at a pressureabove atmospheric pressure and by continuously mixing the reactingsubstances. The object of mixing is to enable the basic agents topenetrate fully into the product and provide intimate contact betweenthem.

Mixing is preferably carried out continuously in an extruder comprisingan endless worm and heated by water, steam or electricity at theprocessing temperature. The length of the worm and its speed of rotationare chosen in dependence on the duration of treatment; which is usuallybetween 1 and 10 minutes. The mechanical pressure produced by theextruding worm maintains the desired physical and chemical conditionsand ensures that the basic agents penetrate fully into the product. Theentire volume is occupied by the mixer, so that there is no free spacein which gases can escape from the mixture and lose contact therewith,as happens during batch operation in an autoclave provided with anagitator.

The product, which leaves the extruder at an elevated temperature, veryquickly loses the amine and some of its moisture. Subsequent dryingreduces the moisture content to between 5 and 10 percent. Drying can beaccelerated by crushing" the extruded product into coarse meal.

The invention will now be further illustrated by the following Examples3-6.

EXAMPLE 3 40 g of slaked lime were mixed with 2,000 g of crushed peanutoil cake containing 1,500 ppb aflatoxin. A solution of l 1 ml of 40percent methylamine diluted in 255 ml water was added to the oil cake.The mixture, which had a pH of approximately 9.7, was formed intopellets which were heated to 140C for '20 minutes in an autoclave (at apressure of approximately 3.5 kg/cm produced by the water vapourpresent). The pelletswere crushed and mixed with a quantity ofphosphoric acid such that the pH of the mixture was brought to 6.5.

The mixture was dried in an oven at 80C until its water content was 7percent. The aflatoxin destruction rate was 97 percent. I

EXAMPLE 4 500 g of peanut meal contaoning 500 ppb aflatoxin were pouredinto a Hobart-type planetary mixer rotating at speed 1. An aqueoustreating suspension was slowly added over a period of approximately 3minutes. The treating suspension was prepared as follows: 6.5 ml of anaqueous solution of 40 percent methylamine (weight/volume of solution)was dilutedv in 125 ml water, g of slaked lime (Ca(PH) were added andthe mixture was agitated to obtain a uniform suspension.

After the suspension had been added to the meal, the substances werefurther mixed for 30 minutes and then continously introduced via a feedworm into a Brabender extruder (Type 826600). The main extruder body andthe extrusion head previously had been heated to 100C by electricheating jackets, the operation of which was regulated by threethermocouples whose temperatures were recorded. The extruder wormrotated at 5 rpm corresponding to thermal treatment of the product for 5minutes. Detoxification was therefore performed at a pressure ofapproximately 1.5 kg/cm and at a temperature of approximately 110C.

The substance left the extruder in the form of a wet cylinder or rollwhich was dried until its moisture content was about 7 percent. Dryingcould be accelerated by grinding the roll into coarse meal, which wasthen dried.

The dried product had an aflatoxin content of less than 50 ppb (50mg/tonne).

EXAMPLE 5 The method was the same as in Example 4 until the roll havinga moisture content of 7 percent was obtained. The roll was then crushed,and 70 ml of 70 percent phosphoric acid solution was added withagitation to the resulting meal in order to reduce the pH of the productto 7 or below, i.e. to neutralize the product.

EXAMPLE 6 The apparatus used was an industrial extruder modified forfood pastes and having a worm 233 cm long and 13.5 cm in diameter. Amixer disposed upstream of the worm had a capacity of 150 to 200 kg ofoil-cake meal and was able to uniformly mix the basic agents with theoil cake, infected with aflatoxin. The mixer may also be continuouslysupplied with the oil cake and with the basic reagents.

The method was as follows: 3 kg of slaked limed were mixed with 150 kgof peanut oil-cake meal having a particle size of 1 to 3 mm andcontaining 900 ppb of aflatoxin, the mixing process lasting minutes. Aquantity of 2,250 litres of a 40 percent solution of methylamine wasdiluted in 25.2 litres of water and added to 6 the oil cakein-fractions,between which mixing was continued. for about} m inute..After all thesolution had been added, mixing wascontinued forabout 1.0, to 15minutes. The extrusion process, which was-carried out at 110 to 112C,and passage throughthe extruder lasted for about 5 minutes. .Theresulting destruction rate of aflatoxin. was of the order-of percent.

As the preceding shows, the method according to the invention ispreferably continuous. The method can substantially reduce the lengthand cost of treatment a. forming a homogeneous mixture comprising; the Icrushed product, from 10 to 40 percent by weight of water, at least onebasic agent selected from the group consisting of the oxides andhydroxides of alkali metals and alkaline earth metals in an amount suchthat the homogeneous mixture has a pH of least 8, and at least oneorganic amine in an amount sufficient to further raise the pH to atleast 9.5;

b. reacting the homogeneous mixture by maintaining the product at atemperature between room temperature and 150C for a time sufficient toreduce the aflatoxin content of the product to less than ppb; and

c. drying the resulting detoxified product to reduce its water content.

2. The method according to the claim 1, wherein the amount of organicamine in the homogeneous mixture is from 0.1 to 0.6 percent by weight.

3. The method according to claim 1, wherein the homogeneous mixture ismaintained at a temperature below C for a time sufficient to reduce theaflatoxin content in the product to less than 50ppb.

4. The method according to claim 1, wherein the mixture is reacted at apressure greater than atmospheric pressure.

5. The method according to claim 4, wherein the mixture is continuouslymixed during the reaction.

6. The method according to claim 1, wherein the reaction is carried outat a temperature between 70 and 150C and at a pressure greater thanatmospheric pressure, and the mixture is continuously mixed duringreaction.

7. The method according to claim 1, wherein the product is peanut oilmeal,

8. The method according to claim 1, wherein the organic amine isselected from the group consisting of methylamine, dimethylamine,trimethylamine and ethylamine or mixtures thereof.

9. The method according to claim 1, wherein the basic agent is selectedfrom the group consisting of calcium oxide, calcium hydroxide, sodiumhydroxide and potassium hydroxide.

10. The method according to claim 5, wherein an extruder having anendless worm is used for mixing, and the speed of rotation of the wormis such that the duration of reaction is from 1 to 10 minutes.

' sufficient to bring the pH of the product to a value not 8 exceeding7.

14. The method according to claim 1 wherein said homogeneous mixture ispelletized prior to the reacting of said mixture.

15. The method according to claim 1 wherein said dried detoxifiedproduct is formed into feed oil cakes.

1. A METHOD OF REDUCING THE AFLATOXIN CONTENT OF AN AFLATOXIN CONTAINEDOILSEED PRODUCT HAVING A FATS CONTENT LESS THN 10 PERCENT, WHICHCOMPRISES THE STEPS OF: A. FORMING A HOMOGENEOUS MIXTURE COMPRISING; THECRUSHED PRODUCT, FROM 10 TO 40 PERCENT BY WEIGHT OF WATER, AT LEAST ONEBASIC AGENT SELECTED FROM THE GROUP CONSISTING OF THE OXIDES ANDHYDROXIDES OF ALKALI METALS AND ALKALINE EARTH METALS IN AN AMOUNT SUCHTHAT THE HOMOGENEOUS MIXTURE HAS A PH OF LEAST 8, AND AT LEAST ONEORGANIC AMINE IN AN AMOUNT SUFFICIENT TO FURTHER RAISE THE PH TO ATLEAST 9.5; B. REACTING THE HOMOGENOUS MIXTURE BY MAINTAINING THE PRODUCTAT A TEMPERATURE BETWEEN ROOM TEMPERATURE AND 150*C FOR A TIMESUFFICIENT TO REDUCE THE AFLATOXIN CONTENT OF THE PRODUCT TO LESS THAN100 PPB; AND C. DRYING THE RESULTING DETOXIFIED PRODUCT TO REDUCE ITSWATER CONTENT.
 2. The method according to the claim 1, wherein theamount of organic amine in the homogeneous mixture is from 0.1 to 0.6percent by weight.
 3. The method according to claim 1, wherein thehomogeneous mixture is maintained at a temperature below 150*C for atime sufficient to reduce the aflatoxin content in the product to lessthan 50ppb.
 4. The method according to claim 1, wherein the mixture isreacted at a pressure greater than atmospheric pressure.
 5. The methodaccording to claim 4, wherein the mixture is continuously mixed duringthe reaction.
 6. The method according to claim 1, wherein the reactionis carried out at a temperature between 70* and 150*C and at a pressuregreater than atmospheric pressure, and the mixture is continuously mixedduring reaction.
 7. The method according to claim 1, wherein the productis peanut oil meal,
 8. The method according to claim 1, wherein theorganic amine is selected from the group consisting of methylamine,dimethylamine, trimethylamine and ethylamine or mixtures thereof.
 9. Themethod according to claim 1, wherein the basic agent is selected fromthe group consisting of calcium oxide, calcium hydroxide, sodiumhydroxide and potassium hydroxide.
 10. The method according to claim 5,wherein an extruder having an endless worm is used for mixing, and thespeed of rotation of the worm is such that the duration of reaction isfrom 1 to 10 minutes.
 11. The method according to claim 10, wherein theextruded detoxified product is crushed before drying.
 12. The methodaccording to claim 1, wherein the detoxified product is dried to amoisture content of from 5 to 10 percent.
 13. The method according toclaim 12, wherein phosphoric acid is added to the dried product in aquantity sufficient to bring the pH of the product to a value notexceeding
 7. 14. The method according to claim 1 wherein saidhomogeneous mixture is pelletized prior to the reacting of said mixture.15. The method according to claim 1 wherein said dried detoxifiedproduct is formed into feed oil cakes.